Galvanometer



- struments. 4

35 pins and strips.

d of the instrument.

Patented Augt 15, 1939 I w l UNITED 'ZSTATES PATIENT- OFFICE GALVANOMETER Harry A. Gill, Foxboro, and 'Ralph'H. Baker, At-

tleboro Falls, ,Mass., asslg'nors to The Foxboro Company, Foxboro, Mass, a corporation, of Massachusetts Application-May 17, 1937, Serial No. 142,990

15 Claims. (01. 111-95) This invention relates to galvanometers of the ing it, the benefit on a snubbing' action is obs, 'dArsonval type and more particularly relates totained.

means for. mounting the moving coils of suchin- This and other apparent objects and advanv v tages are obtained by the means described in the In galvanometers of the dArsonval type, in following specification, and may be'more readily -5. order to avoid the loss of sensitivity due to pivot" understood by reference to; the accompanying friction encountered when a jew'elled pivot type of drawing in which: mounting is used, it has been customary to sus- Figure 1 shows a front elevation of a galvanom pend the moving coil of such a meter between eter coil mounted in accordance with the method suita le supports by two torsionally resilient verof this invention; 7 0

tical' strips. These suspension strips are delicate Figure 2 shows a side view of the galvanometer and are under considerable tenslon.- They must arrangement shown in Figure 1;. 7 be firmly attached to the armature and to the Figure '3 shows an enlarged view in perspective support to prevent variations in the adjustment of the way in which'the suspension strip is atof the instrument and also to provide a"good tached to'the lower part of the coil illustrated in 15 electrical connection to the galvanometer coil be- Figure 1; v r

cause these strips are usually used to conduct the Figure 4 shows an enlarged view in perspective current flow to and from the coil. of a suspension 'strip connector in accordance with a In the past it has beencustomary to solder one embodiment of this invention; v these strips directly to a portion of the coil Figure 5 shows a plan view of the connector mounting and to the supports. Such an arrangeillustrated in Figure 4; ment is somewhat impractical because it neces- Figure 6 is a section taken through line-6 -6 oi 'sitates the services of a trained operator to re-- Figure 5; place the suspension-strips in the event that they Figure .7 is a plan viewof another. embodiment v215 are damaged, broken or for some other reason of this invention; and need replacing-To overcome this difficulty it has FigureB is a section taken on line 8-8 of been customary permanently to attach connectors Figure]. i in theform of pins to the endsof the suspension Referring to Figures 1 and 2 the movingcoil 2 strips adapted to connect detachably with the of a galvanometer, provided with a pointer 4 coil frame and the supports. However, this type rigidly attached to the top thereof, is suspended; 3

of pin connection and the manner of securing the on two torsionally' resilient metal suspension pin to the strip has proven unsatisfactory because strips 6- extending betweentwo supports 8 which of the difficulty of assembling the'parts and the subject the strips toa resilient tension. The supa susceptibility to breakage atthejunction'of the; ports 8 are preferably provided with means,'not

In the present invention this manner of coil suspension strips-i .are soldered to connectors l0 suspehsion has been improved to make assembly;- which in turn'are firmly clamped "by screws II and disassembly easier and'to make the whole to attaching-faces 13 onfthe supports 8 and on support stronger withoutiinpairingthesensitivityl connection tabs 12 extending axially from coil2.

In accordance with an embodiment of the insliehtly-crqwnedi acylindrical surface, the generat- :vention herein illustrated, a slightly crowned ing element 'of which-is perpendicular to the suscylindrical surface is provided on each connector pension'strip, aroundwhich the strip is snubbed over which surface-the suspension strip passes. before being attached .to the connector.- The 45, The strip leaves the connector tangentto the slight crown to the cylindrical surface'of'the consurface and in a direction perpendicular to the. 'nector is desirable because the greatest strain is generating element of the cylindrical surface, exerted on the center of the strip rather than on whereby the strip is not subjected at any point'to its edges. .In addition, it vpermits the strip to sharp-bending. In this way, too, thesolder or-j swing a small amount in any direction without shown, for adjusting the tension. The ends of the.

Each of the--; connectors I'll provided with a o;

60 other means for attachingthe strip to the conplacing'a strain on the edge of the strip. Each L nector actually is only an anchorage for the end of the connectors-is also provided with a keyholeof the strip, and no. forces'are exerted on the shaped slot through which a' screw passes to clamp strip at this connection other than along the line the connectorto the attaching face, andan offset r of the curved surface. Further, by passing the portion to, coact'with the attaching face to aid 65 strip around such a curved surface before anchorin accurately positioning the connector with respect to the attaching face to which it is clamped.

Figures 4, 5 and 6 show a connector which is one embodiment of this invention. This connector may be stamped out of sheet metal and is provided with a tongue l8 stamped out of the body of the connector and curved away from the connector to form a slightly crowned cylindrical surface I! tangential to the body of the connector as is more clearly, shown, in Figure 6. The suspension strip, shown in broken line 6 in Figure 6, passes around this curved surface I! and is soldered, welded or anchored in any other suitable manner to the end of the tongue l6 at an anchoring portion 28.. The curved surface I1 is continued to the end 22 of the connector where the tongue l6 joins the body of the connector, so that the strip 8 leaves the curved surface I! tangentially and never makes contact with a sharp corner (as at the end 22 of the connector) which might cause the strip to bend sharply and tend to damage it, causing it to break at this point.-

The other end of the connector is expanded slightly and is provided with two intersecting holes 24 and 26 forming a keyhole-shaped slot. The diameter of the hole 24 is slightly larger than the diameter of the head of the clamping screw l4 and the diameter of hole 26 is smaller than the diameter of the head of the screw H but slightly larger than the shank of the screw. This end of the connector is also provided with a small offset portion or lip 28 which fits into a slot 38 in the attaching face I 3 of the coil connection tab I 2, as is more clearly illustrated in Figure 3, to aid in properly positioning the connector with respect to the attaching face.

In the embodiment shown in Figures 1 through 6, the portion of the connector to which the tongue I6 is attached is slightly offset with respect to the other portion of the connector by a bend 23 so that the point 32 where the strip meets the connector is in the same plane as the face 84' of theconnector which is adjacent the attaching face l3 when the connector is clamped in position. Thus the longitudinal pull on the suspension strip is in the same plane as the attaching face of the coil tab l2 or the support 8. This arrangement is also advantageous where it is desired to have the line of pull of the suspension strips pass directly through the geometrical center of the galvanometer coil 2 becausethe bend 23 maybe so designed as to accomplish this result regardless of the thickness of the connection tab l2. In addition it permits the tongue IE to extend toward the back of the galvanometer assembly.

In galvanometer suspensions of the type herein described, it is important that the delicate suspension strips, which are usually made of a gold alloy, do not come into contact with any irregular surfaces which might tend to bend or damage 70 some smoothing process such as a tumbling operation, and'finally to plate them with a layer of pure gold. This gives the connectors a smooth and highly polished surface which is extremelyv resistant to corrosionand to which the suspension strips may be readily soldered or welded.

I In attaching a suspension strip to the anchoring portion 28 of the curved surface I! of a connector care must be taken to avoid solder running around the curved surface so as to form a connection between the strip and the surface atany place near the point at which the strip departs tangentially from the surface. Otherwise forces other than those longitudinal of the strip may be exerted on the strip when the galvanometer assembly is subjected to forces other than those electrical forces rotating the armature.

With suspension members of this type, the mounting of a galvanometer coil may be accomplished very readily and without difficulty. The' clamping screws II on the galvanometer coil connection tabsl2 and on the-supports 8 are loosened, the connectors are slipped er these screws by means of the large holes 2 and are then moved along under the heads of the screws until the shanks of the'screws fit into the smaller holes 26. They are then clamped tightly against the attaching faces III by tightening the clamping screws I 4. The keyhole-shaped slots in the connectors permit the connectors to be hooked in position and clamped to the attaching faces IS without removing the clamping screws l4 therefrom, and, in connection with the lips 28 on the ends of the connectors, they hold the suspension members in their properpositions so that the galvanometer assembly is operative even though the clamping screws H be loose.

A connector forming another embodiment of this invention is shown in Figures '7 and 8. In this connector a cylindrical bar 38 is clamped in place by two arms '40 and 42 extending from the body of the connector. The suspension strip 6 is snubbed around the cylindrical surface of this bar and is attached to the end of a third arm 44, substantially as shown.

As connectors of various forms may be constructed and various modifications may be availed of without departing from the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative only and not in a limiting sense.

We claim: K a

1. In a galvanometer suspension system of the type wherein a moving galvanometer armature is suspended to rotate on an axis, between two delicate suspension strips extending from opposing supports, connectors for joining the ends of each suspension strip respectively to the armature and support, each connector comprising, in combination, a cylindrical snubbing surface, an anchoring surface adjacent and tangent to said snubbing surface to which the strip end is connected, and each connector having a keyholeshaped opening adapted to pass over the head of a supporting screw and'to slip down over the shank thereof whereby said connectors'may be held in place so that the strip passing from the connector leaves it tangentially and perpendicular to the element generating the cylindrical surface.

' supports, connectors for joining the ends of each suspension strip respectively to ,the armature and support, each connector comprising, in combination, a. body portion having a struck-up tongue forming a snubbing surface and an anchoring surface, a cut-out portion for receiving a supporting screw, and an offset portion adapted to coact with a slot in the support to which the c'onnectoris attached to align the same with said support. v

3. In a galvanometer suspension system of the type wherein a moving coil member-of a galvanometer is .rotatably suspended'about an axis on two delicate suspension strips extending from said coil member to two suitable supports, the combination of connectors for joining said strips to said coil member, means for detachably connecting said connectors to said coil member, and

means to aid in the positioning of said connectors with respect to said coil member including offset oortions on said connectorsadapted to coact with slots in saidcoil member.

4. ..In a 'galvanomet'er suspension system of the type wherein a moving coil member of a galvanometer is suspended .on an axis on two delicate suspension strips extending from said coil member to two suitable supports, in-combination, connectors for joining said strips to said coil member and supports, means for detachably connecting said connectors to said coil member and supports, and means to aid in the positioning of said connectors with respect to said coil member and supportsincluding flat tabs bent away from the bodyof said connectors adapted to coact with straight edges on said coil member and supports perpendicular to the axis of said 'galvanometer suspension.

5. A connector for connecting the end of a stripsupporting a galvanometer armature to either the'armature or the support, comprising a strip-connecting portion having a struck-up .tongue, the tongue and end portion of said stripconnecting portion being curved and provided with a crowned surface and the end of said struckup tongue being curved slightly toward said end portion, and a mounting portion having a keyhole-shaped opening adapted to pass over a headed screw and to slip over the shank thereof to hold the connector so that the strip leaves the struck-up tongue portion tangentially.

6. A connector for connecting the end of a strip supporting a galvanometer armature to either the armature or the support, comprising a strip connecting portion having a struck-up tongue, the tongue and end portion of said strip-connecting portion being curved and provided with a crowned surface and the end of said struck-up tongue being, curved slightly toward said end portion,

and a mounting portion having a keyhole-shaped opening adapted to pass over a headed screw and to slip over. the shank thereof to hold the connector so that the strip leaves the struck-up tongue portion tangentially, said'connector being formed from bronze and having a 14 karat gold plating covered by a pure gold plating.

'7. A connector for connecting the end of a. strip supporting a galvanometer armature either to the armature or the support, comprising, in combination, an end portion cut into three fingers, the outer two of which are bent to form bearings, a pin held in said bearings, and the middle finger bearing downwardly against said pin, said middle finger being adapted to form an anchorage to which the strip is attached, the

strip then passing over the pin which forms a snubbing surface, said connector also having a supporting portion by whichthe connector is attached to the armature or support.

8. For use in a meter assembly having an armature and a delicate suspension strip for said armature, means for securing an end of said strip toa portion of said assembly, comprising, in combination, a. convex cylindrical snubbing surface over which the suspension strip passes in leaving said means, and an anchoring surface on said cylindrical snubbing surface removed from the point at which said strip leaves the snubbing surand a delicate suspension strip for said armature,

in combination, a connector for joining an end of said strip to a portion of said assembly, means for detachably securing said connectorto said portion, and means for aiding in the positioning of said connector with respect to said portion including a projection and a positioning surface adapted to coact therewith, one of said lastnamed elements beingassociated with said connector and the other with said portion.

11. A meter assembly, including, in combination, a moving armature suspended between two delicate suspension strips extending from'opposing supports, and means for joining the ends of armature, each of said means having a convex cylindrical snubbing surface over which its suspension strip passes in leaving said means.

12. A meter assembly, including, in combination, a moving armature suspended between two delicate suspension strips extending from opposing supports, connectors for joining theends of each strip respectively to its-support and to said armature, each of said connectors having a convex cylindrical snubbing surface over which its suspension strip passes in leaving said connector, and means for detachably securing said connectors to said armature and supports.

13. In a meter assembly having an armature and adelicate suspension strip for said armature,

30 each strip respectively to its-.support and to said in combination, means for securing an endof I saidstrip, and a convex cylindrical snubbing surface over which said strip passes in leaving said means, said means and cylindrical surface being so arranged that the strip contacts the snubbing surface throughout an arc of approximately120" or more.

14. For use in a meter assembly having an armature and a delicate suspension strip for said armature, means for securing an end of said strip to a portion ofsaid assembly, said means comprising, in combination, anchoring means for anchoring said end, a convex cylindrical snubbing surface so positioned that said strip passes from said anchoring means in a tangent to said snubbing surface, passes over a portion of said snubbing-surface, and leaves said snubbing surface tangentially, and means to prevent said strip from being moved inadvertently from its tang'ential path between said anchoring-surface and said snubbing surface.

15. In a meter assembly having a moving armature, asupport therefor, a delicate suspension strip for supporting said armature from said support, and means for maintaining said suspension strip under tension, in combination, a

connector securedto an end of said strip for attaching said strip to a connection portion of said support and means for detachably' securing said connector to said portion including means said position in spite of the tension exerted on for hooking said connector to said portion and said strip until said connector is rigidly clamped aligning it therewith in a given position, and to said connection portion of said support in said means for clamping said connector to said poraligned position.

tion to maintain it in said aligned position, said HARRY A. GILL. hooking means serving to hold said connector in RALPH 1-1.. BAKER. 

